of chicago



Patented May 1, 1928.

UNITED STATES PATENT OFFICE.

J BIRCHARD GREEN, OIE CIIICAGO, ILLINOIS, ASSIGNOR 'I'O CHICAGO STEEL & WIRE COMPANY, OF CHICAGO, ILLINOIE, A CORPORATION OF ILLINOIS.

STITCI'IING WIRE.

No Drawing.

My invention relates to steel wire for stitching and more particularly to flat wires for stitching cardboardboxes, fiber contain ers, and the like. It is desirable to have this wire quite stiff but this stillness must be produced by cold work on comparatively low carbon steels and not through higher carbon or other alloy content. The stiffer the wire the greater thickness of stock it will puncture. The higher the carbon content the quicker the cutter knives in the stitching machine will dull, and only slight dullness is required to leave a burr on the puncturing end of the legs of the stitch or staple thus seriously interfering with driving it through the stock. In addition to these requirements, atleast the outside fibers of the stitching wire must be siiifiiciently ductile to permit the clinching of the stitch without cracking the wire.

These several requirements have been met in the past by using what is known a rimmed steel of about 08% carbon content, cold-drawing it as a round wire according to well-known wire-mill practice to give the correct temper and then flattening it by cold rolling to about .103 width and a variety of thicknesses from .023 to .017 inclusive and occasionally as light as .0887 such as will permit satisfactorily stitching in the range of work met with in practice.

The wire must be flat because it is cousidcred desirable that the wire stitch lay practically flush with the surface of the stock. A round wire would protrude substantially above this surface unless buried in the stock by force and such action would result in weakening the material at the point of stitching thus reducing the carrying capacity of the box or container.

A characteristic of rimmed steel is the form of the carbide, which is essentially pearlitie in the center portion and globular in the outer or rim portion. Carbon steels in which the carbide is in globular form take temper very little with cold work, while those with the carbide in pearlitic form take temper to a marked degree with cold work. The mashing flat of a round wire by cold rolling appears to have comparatively little embrittling elfect until the width passes about three times the thickness from which .Applicatien filed January 20, 1927. Serial. No. 162/119.

point it increases rapidly and at about five times becomes very pronounced. This ac counts for the necessity of using rimmed steel for stitching wires approximately .103 in width and .023" or less in thickness. It permits producing a wire with. a stiff center and a ductile shell or surface. If a steel. essentially pearlitic were employed, it is commercially impossible to produce the desired stiffness and surface ductility at the same time. Either can be produced alone but not both coincidenti-illy.

The wire characteristics and proportion above described have always been recognized in the industry as the fixed standards for wire used for stitching card board boxes, fiber containers, and the like.

I have discovered that by combining the use of low carbon steel of .520 points or less carbon, the resultant carbide being essentially in pearlitic form, with wire dimensions such that the ratio of width to thickness does not substantially exceed four to one nor substantially less than one and three quarters to one, that all the requirements of be}; stitching wire can readily be met. I find that widths from .050" to .070 are satisfactory, and I prefer to use .000 as the most desirable width.

In this manner ll can prmlure a box-stitching wire of substantially the same cross-sectional area as that heretofore in couuuon use and consequently the same number of feet per pound but with far greater puncturing power, or ll an hold the puncturing power substantially the same as that of the wire heretofore in common use and, by re ducingthe cross-sectional area so that its moment of inertia corresponi'lsto a size heretofore in common use, produce a wire with far more lineal feet per pound.

I claim:

As an article of manufacture, a that carbon steel stitching wire, the carbide being essentially in pearlitic form, and the ratio of width to thickness not substantially exceeding three to one or substantially less than.

one and three-quarters to one.

In testnnony whereof I have hereunto subscrlbed my name.

J BIRCHARD GREEN. 

